1. Field of the Invention
The present invention relates to a soft magnetic stainless steel for cold forging, having excellent formability in cold forging, machinability, electrical and magnetic properties, and corrosion resistance, and suitable for use as a material for stationary cores and movable cores of solenoid operated valves and electromagnetic clutches, and bodies of electronic fuel injection apparatuses for internal combustion engines.
2. Description of the Prior Art
Conventionally, soft magnetic stainless steels must have prescribed magnetic properties (e.g., magnetic flux density, and coercive force), electrical resistance, corrosion resistance, machinability, and the like. In order to obtain particularly excellent magnetic properties, 2Si-13Cr steels, 1Si-0.20Al-13Cr steels, and the like have been proposed and some of them have been put into practical use. The application field of soft magnetic stainless steels has recently been widened, and more soft magnetic stainless steels are applied to parts having complex shapes such as bodies of electronic fuel injection apparatuses and cores of solenoid operated valves and electromagnetic clutches. In view of this, a demand has arisen for a soft magnetic stainless steel which has excellent formability in cold forging and excellent machinability in addition to other properties as mentioned above.
In response to this demand, for example, a steel has been proposed wherein the C content in a 1Si-13Cr-0.2Al steel or the like is reduced to about 0.01%, and 0.018% of S and 0.2% of Pb are added, and some of such steels have already been put into practical use.
These steels, however, still do not have completely satisfactory formability in cold forging; they have a tensile strength of 44.5 kgf/mm.sup.2, a reduction of area of 74%, and a critical compressibility of 47%. Therefore, these steels cannot be subjected to cold forging for manufacturing parts having complex shapes such as bodies of electronic fuel injection apparatuses. Accordingly, a soft magnetic stainless steel having both excellent formability in cold forging and machanability and excellent electrical and magnetic properties has been desired.